Electrical earphone device



G. D. CHICHESTER 2,565,591

ELECTRICAL EARPHONE DEVICE Aug. 28, 1951 Filed Oct. 5, 1946 Fig. 3.

Radio or P.A. Output Circuit 32 INVENTOR George D. Ghichestar BYATTORNEYS Patented Aug. 28, 1951 ELECTRICAL EARPHONE DEVICE George D.Chichester, Pittsburgh, Pa., assignor to Pentone, Inc., Pittsburgh, Pa.,a corporation of Pennsylvania Application October 1946, Serial'No.701,468

8 Claims.

This invention relates to an accoustical device which is particularlyuseful as an electrical receiver or earphone, although the device isalso useful in transmitting apparatus and the like.

In the past, electrical receivers have almost 'invariably included adisk-shaped diaphragm which would become distorted in response tomagnetic field fluctuations caused by voice modulated currents and thelike passing through an electromagnet coil. Such types of receivers havethe outstanding objection of being somewhat cumbersome in construction,expensive to manufacture, and relatively heavy-furthermore, such typesof receivers lack fidelity in reproduction due to the varying degrees offlexibility of the diaphragm at different portions thereof, and therestraining effect caused by clamping of the peripheral edge, also dueto the damping effect caused by accidental touching of the vibratingdiaphragm.

An object of this invention, therefore, is to provide an electricalreceiving apparatus that is devoid of the above-named disadvantages ofcommon types of receiving apparatusmore specifically, to provide areceiver that is relatively simple in construction, inexpensive tomanufacture and which possesses a high degree of fidelity. I

Another object of this invention is to provide an electrical receivingapparatus which includes a pair of permanent magnets arranged so thatlike poles are in confronting relationship.

A further object of this invention is to provide an electrical receiverwhich is devoid of a diaphragm of the usual type and which may employeither a metallic housing or a diaphragmlike metallic disk, theoperation of which, however, is somewhat different from that of theoperation of the well-known diaphragm.

A further object of this invention is to provide a hermetically sealedhousing enclosing a novel permanent magnet type of receiver which may besubstituted for the voice coil of a conventional type loud-speaker of aradio whenever reception at lower volume is desired.

A still further object of this invention is to provide a novel typeelectrical receiver which is of such construction as to emit practicallyno sound when used alone, but whose volume is increased by placementclosely thereto, in con tacting relationship, a pillow or similardevice, thus providing a means for individual radio reception to allow,for example, a hospital patient to listen to broadcasts from thereceiver located under his pillow without disturbance to nearbypatients.

Other objects and advantages of this invention will become apparent froma study of the 2 following specification taken with the accompanyingdrawings wherein:

Fig. 1 is a schematic electrical wiring diagram showing an electricalreceiver in cross-section which embodies the principles of thisinvention;

Fig. 2 is a plan view of the spider included in the receiver shown inFig. 1;

Fig. 3 is a cross-sectional view taken along line III-III of Fig. 1;

Fig. 4 is a front view of a radio receiver showing a switch forselectively connecting either the speaker or receiver in the circuit,and c Fig. 5 is a wiring diagram including a crosssectional view of amodified form of receiver which may be substituted for the one shown inFig. 1.

Referring more particularly to Figs. 1, 2 and 3, numerals I and 2 denotea pair of permanent magnets of any suitable material of high magneticpermeability, such as an alloy of aluminum, nickel and cobalt, whichmagnets may be in bar form, as shown, or of any other suitable shape.The magnets may be wrapped with tape to serve as insulating spacingmaterial and are arranged so that like poles will be in confrontingrelationship. As shown in the drawing, the two north poles are closelyspaced and face each other so as to provide a magnetic fieldtherebetween.

A spider 3 made of any suitable material, such as paper, or otherinsulating material, is formed so as to have an odd number of radiallyextending tines or arms, such as 4, which tines serve as supports for acoil 5 which is wound somewhat in pancake form on the spider and whichis woven in wave-like or basket-weave form alongside the tines. An oddnumber of tines, such as H, is preferably provided for the purpose ofhaving successive turns of coil 5 arranged so as to be located onopposite sides of any individual tine. It should be understood, however,that the coil may take other shapes, such as a spiral shape, preferablyin a flat plane. Successive turns of coil 5 are shown spaced forillustration but in reality are fine wires in contacting relationship.

The housing comprises a cup-shaped portion 6 and a cover portion 1sealed thereto so as to provide a hermetically sealed enclosure. Ametallic disk-shaped diaphragm 8 is supported on a spacer ring 9 whichin turn rests on an annular raised portion of the housing portion 6. Ifthe spacer ring 9 is made of rubber, deeper tones are obtained than ifit were made of hard material, such as plastic or metal, in which caseshigher tones are obtained. Thus by proper selection of the spacermaterial, the desired pitch may be obtained. If desired, spacer 9 may beomitted altogether. Diaphragm 8 has supported thereon an annular gasketIll serving as a spacer element between the diaphragm and spider 3. Aninsulating ieet or spacer H is rested on spider 3. The poles I and 2 mayrest on spacer H. An insulating spacer or sheet l5 may be interposedbetween the magnets and cover 1. Such spacer may be omitted, however, ifdesired. A plug 12 may be used which is adapted to cooperate with a jack(not shown) in a radio receiver set. Plug 12 is connected by lead-inwires I3 to coil 5, which wires are introduced into the receiver devicethrough a grummet l4. Thus there is provided a compact assembly whereinthe parts are in close, substantially contacting relationship so as tobe able to transmit motions therebetween and allow the entire assemblyto vibrate or operate in unison. In operation, it appears that thediaphragm vibrates without apppreciable flexing together with theremainder of the assembly;

Figs. 4 and 5 show a modification wherein a metallic housing, instead ofa plastic or insulating housing, is used, comprising a body portion H3and a fiat diaphragm-like end or cover portion ll for enclosing the coiland magnets. The housing parts are preferably hermetically sealedtogether by soldering or the like in order to provide best results inreception. Hermetic sealing excludes moisture and deleterious gases fromthe atmosphere which may attack the insulation or magnetic parts.

A small air gap or clearance is provided between cover portion l1 andthe magnets, that is, the tape or wrapping about the magnets. An

annular paper gasket 22 and a sheet of insulating material 23 areinterposed between the poles and spider-coil assembly. If desired, sheet23 may be eliminated and reliance may be made on the insulating wrappingabout the magnet poles. An annular insulating spacer B l is interposedbetween the spider-coil assembly C a5a and body portion iii of thehousing. Spacer 2d may be eliminated by providing a shoulder at theperiphery of portion l5 similar to the shoulder on portion 6 shown inFig. 1. All the spacers or gaskets are preferably very thin so as toprovide very close spacing between the respective elements and provideelectrical insulation therebetween and for the purpose of making theentire assembly very compact in construction. If desired, the entireoutside surface of the metallic housing Iii-41 may be enameled, paintedor otherwise coated with insulating or metallic material. The spider andthe magnets may be secured together, with their intervening spacingmaterial, as a single I unit.

The theory of operation of the above-described receiver is not toowell-known, however, experiments appear to indicate that the housingportion I! does not distort or flex by diiferent amounts at dififerentareas of the surface under electromagnetic variations in the manner ofthe well-kn0Wn type of metallic diaphragm, but instead it seems as ifthe entire housing vibrates in unison together with the enclosed partsin response to electrical current variations flowing through coil 5a.This conclusion is arrived at principally because no material difierenceappears to result from the touching of housing portion I! with oneshands, which touching would have a serious damping effect on an ordinarytype of diaphragm.

Of course, the magnetic lines of force which emanate from the like northpoles of permanent magnets la and 2a will buck each other, conseiii)quently will diverge outwardly from the mid-point between theconfronting poles and will find a return path to the opposite polesthereof through portions of the housing. The magnetic field developed.by the current flow through the coil windings is toroidal in form andencircles the coil 5a. The interaction of the two fields provides anelectromagnetic efiect which apparently causes vibration of the entireassembly, which results in the emanation of sound corresponding to thatof the signal current passing through coil 5a. The housing should bemade of relatively thin metal, preferably not thicker than thirty-fivethousandths inch. By making the housing of thinner material, less of thebase notes of radio reception are heard. Coil 50. should be very tightlywound about the spider and preferably lacquered to effect stiffening ofthe coil to provide a spider-coil assembly having no individuallymovable parts so as to prevent harmonics. Such coating also makes theunit waterproof and moisture-proof.

The electrical receiver described is admirably adapted as a componentpart of a radio set for the purpose of allowing an individual toselectively obtain reception either from the loudspeaker of the radioset or from the receiver at will. It is also very useful in publicaddress systems.

A convenient circuit is provided, in the case of use with a radioreceiver, by having primary winding 29 of an output transformer, whichis connected to the output of radio 27, for example, and which is ofhigh electrical impedance (of the order of 550 ohms) cooperate with asecondary winding 3% of relatively low impedance (of the order of 4ohms), which secondary winding is normally connected to the voice coil3! of a loud-speaker 32 of the radio set. A switch 33 may be providedfor the purpose of selectively connecting the secondary winding 38either to voice coil 3! for normal radio reception, or to coil Ea of theabove-described receiver for relatively silent reception so as to enablethe operator to listen to the receiver without disturbing personsnearby, such as under a pillow.

The average voltage applied across the coil may be only of the order of1.5 volts. Thus it will be seen that the receiver device consumes aninsignificant amount of power.

If desired, the housing of either Fig. 1 or Fig. 5 may be partiallyevacuated and filled with an inert gas, such as a noble gas;furthermore, instead of providing a switch 33, as shown in Fig. 5, ajack may be provided which may be mounted on the side or panel of aradio set so that when a plug, such as l2 in Fig. 1, is inserted in thejack, the circuit to the voice coil of the speaker is broken, whereasthe circuit to the coil of the receiver unit is made. Likewise, othervariations will be readily suggested to those skilled in the art to makethe above-described receiver useful for the purpose intended. It shouldbe noted that not only pillows serve as media for enhancing the soundemitted from the above-described novel receiver, but other objects, suchas flat panels, doors, desks or the like, also have somewhat of anenhancing effect when the receiver is placed in contacting relationshiptherewith. It will be apparent to those skilled in the art that theabove-described receiver can be used in aiding partly deaf people andmay be worn on ones clothing, such as on a lapel of a coat, or may beadapted so as to be worn on the ear or in the car, as is well-known inthe art. The abovedescribed speaker can be made smaller and isparticularly adapted to be reduced in size rather easily because of itsextreme lightness and simplicity of construction. An enhancing effect onthe volume is obtainable by contacting the receiver with a part of thebody, such as the ear.

Thus it will be seen that the above-described permanent magnet receiverprovides a highly eflicient, inexpensive type of receiver (ortransmitter) which is particularly useful as a relatively silent meansto provide individual radio reception without disturbing nearby personsby virtue of the fact that the receiver is of such construction that itsemanating tones or signals are confined and enhanced or made louder byplacement of a pillow or similar object in con tacting relationshiptherewith; furthermore, I have provided a receiver whose outstandingqualities are apparently attributed to the fact that it does not involvethe well-known distortion effect of common types of receiver diaphragms,but instead appears to embody the idea of an entire assembly vibratingin unison for emitting sound.

While I have illustrated and described certain specific embodiments ofmy invention, it will be understood that this is by way of illustrationonly and that various changes and modifications may be made within thecontemplation of my invention and within the scope of the followingclaims.

I claim:

1. Electrical receiving apparatus comprising a pair of opposed permanentmagnet poles of the same polarity, a metallic diaphragm disposed inspaced parallel relationship alongside said poles, and a coil wound inpancake form in a plane parallel to and interposed between that of thepoles and diaphragm, said coil being wound on a spider having an oddnumber of radially extending tines onto which the coil is wound inwave-like form, successive windings being wound on opposite sides of anygiven tine.

2. Electrical receiving apparatus comprising a pair of permanent magnetshaving opposed poles of the same polarity, a coil disposed alongsidesaid poles and wound in a plane parallel to that of the poles, and ametallic housing totally enclosing said poles and coil, said housingbeing of thin sheet metal, said coil being wound on a spider having anodd number of radially extending tines onto which the coil is wound inwavelike form, successive windings being wound on opposite sides of anygiven tine.

3. An electrical receiving device comprising a pair of flat permanentmagnets disposed so that like poles thereof are in confrontingrelationship, a coil disposed along side said poles in a planesubstantially parallel thereto, a thin metallic hermetically sealedhousing totally enclosing said poles and coil, and a plurality of thinspacer elements for separating said coil and poles from each other andfrom the housing.

4. An electrical receiving device comprising a pair of flat permanentmagnets disposed so that like poles thereof are in confrontingrelationship, a coil disposed alongside said poles in a planesubstantially parallel thereto, a thin metallic hermetically sealedhousing totally enclosing said poles and coil, and having at one side adiaphragm portion disposed alongside and in closely spaced relationshipto said poles and having at the other side a portion of reduced diameteras compared to said diaphragm portion for enclosing said coil.

5. An electrical receiving device comprising a pair of flat permanentmagnets disposed so that like poles thereof are in confrontingrelationship, a coil disposed alongside said poles in a planesubstantially parallel thereto, a thin metallic hermetically sealedhousing enclosing said poles and coil, and having at one side adiaphragm portion disposed alongside and in closely spaced relationshipto said poles and having at the other side a portion of reduced diameteras compared to said diaphragm portion for enclosing said coil, said coilbeing wound on a spider having an odd number of radially extending tinesonto which the coil is wound in Wave-like form, successive windingsbeing wound on opposite sides of any given tine.

6. An electro-acoustical device comprising a spider having a pluralityof radially extending arms, a coil spirally wound on said arms in theform of a single layer in a single plane, and a pair of permanent barmagnets insulatingly supported on said spider-coil assembly and havingclosely spaced confronting like poles for emanating magnetic flux inopposite directions and being in a plane parallel to that of the coil.

7. In a device of the character described, a pair of bar magnetsarranged with their magnetic axes in alignment and with adjacent polefaces of like magnetic polarity, a thin flat supporting member on whichsaid magnets are mounted, a coil of a pancake type mounted adjacent saidsupporting member and having windings in a common plane substantiallyparallel to the plane of said supporting member, and a housing memberformed of thin sheet metal forming an enclosure for said magnets,supporting member, and coil.

8. In a device of the character described, a pair of bar magnetsarranged with their magnetic axes in alignment and with adjacent polefaces of like magnetic polarity, a thin fiat supporting member on whichsaid magnets are mounted, a coil of the pancake type mounted adjacentsaid suppbrting member and having windings in a common planesubstantially parallel to the plane of said supporting member, and ahousing member formed of thin sheet metal forming an enclosure for saidmagnets, supporting member, and coil, said housing member providing adiaphragm responsive to current changes in said coil.

GEORGE D. CHICHESTER.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 281,240 CheeverJuly 17, 1883 1,331,469 Kraft Feb. 17, 1920 1,581,162 Boucher Apr. 20,1926 1,654,741 Lindsey Jan. 3, 1928 1,743,453 Hillhouse Jan. 14, 19301,830,160 French et al Nov. 30, 1931 1,879,612 Hudd Sept. 27, 19321,955,800 Frederick Apr. 24, 1934 1,997,193 Kato et a1 Apr. 9, 19352,341,275 Holland Feb. 8, 1944 2,381,673 Lehde Aug. 7, 1945 2,402,480Zarth June 18, 1946 FOREIGN PATENTS Number Country Date 425,558 GreatBritain Mar. 18, 1935

